Solid suspension and gas dispersion in gas-solid-liquid agitated systems

2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Anna Kiełbus-Rąpała ◽  
Joanna Karcz
Keyword(s):  
Residence Time ◽  
Experimental Studies ◽  
Gas Bubbles ◽  
High Energy ◽  
Gas Velocity ◽  
Solids Concentration ◽  
Three Phase ◽  
Phase Systems ◽  
Superficial Gas Velocity ◽  
Solid Liquid

AbstractThe aim of the research work was to investigate the effect of superficial gas velocity and solids concentration on the critical agitator speed, gas hold-up and averaged residence time of gas bubbles in an agitated gas-solid-liquid system. Experimental studies were conducted in a vessel of the inner diameter of 0.634 m. Different high-speed impellers: Rushton and Smith turbines, A 315 and HE 3 impellers, were used for agitation. The measurements were conducted in systems with different physical parameters of the continuous phase. Liquid phases were: distilled water (coalescing system) or aqueous solutions of NaCl (non-coalescing systems). The experiments were carried out at five different values of solids concentration and gas flow rate. Experimental analysis of the conditions of gas bubbles dispersion and particles suspension in the vessel with a flat bottom and four standard baffles showed that both gas and solid phases strongly affected the critical agitation speed necessary to produce a three-phase system. On the basis of experimental studies, the critical agitator speed for all agitators working in the gas-solid-liquid systems was found. An increase of superficial gas velocity caused a significant increase of the gas hold-up in both coalescing and non-coalescing three-phase systems. The type of the impeller strongly affected the parameters considered in this work. Low values of the critical impeller speed together with the relatively short average gas bubbles residence time tR in three phase systems were characteristic for the A 315 impeller. Radial flow Rushton and Smith turbines are high-energy consuming impellers but they enable to maintain longer gas bubbles residence time and to obtain higher values of the gas hold-up in the three-phase systems. Empirical correlations were proposed for the critical agitator speed, mean specific energy dissipated and the gas hold-up prediction. Its parameters were fitted using experimental data.

scholarly journals Gas hold-up in a three-phase reciprocating plate column

2005 ◽  
Vol 70 (11) ◽  
pp. 1363-1371 ◽  
Author(s):  
Ljubisa Nikolic ◽  
Vesna Nikolic ◽  
Vlada Veljkovic ◽  
Dejan Skala
Keyword(s):  
Solid Phase ◽  
Liquid System ◽  
Column Diameter ◽  
Gas Velocity ◽  
Vibration Intensity ◽  
Three Phase ◽  
Superficial Gas Velocity ◽  
Phase Column ◽  
Plate Column ◽  
Good Agreement

The influence of the geometry of a reciprocating plate column (diameter), superficial gas velocity, vibration intensity and content of the solid phase in the column on the gas hold-up in a three phase column (G-L-S) were investigated in this study. For comparison, the gas hold-up was also analyzed in a gas-liquid system (G-L) in the same type of column. Good agreement between the experimentally determined values of the gas hold-up and those calculated on the basis of the derived correlation for the G-L and G-L-S system was obtained.

scholarly journals The gas holdup in a multiphase reciprocating plate column filled with carboxymethylcellulose solutions

2005 ◽  
Vol 70 (12) ◽  
pp. 1533-1544 ◽  
Author(s):  
Ivica Stamenkovic ◽  
Olivera Stamenkovic ◽  
Ivana Bankovic-Ilic ◽  
Miodrag Lazic ◽  
Vlada Veljkovic ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Power Consumption ◽  
Rheological Properties ◽  
Gas Holdup ◽  
Gas Velocity ◽  
Vibration Intensity ◽  
Three Phase ◽  
Solids Content ◽  
Superficial Gas Velocity ◽  
Plate Column

Gas holdup was investigated in a gas-liquid and gas-liquid-solid reciprocating plate column (RPC) under various operation conditions. Aqueous carboxymethyl cellulose (sodium salt, CMC) solutions were used as the liquid phase, the solid phase was spheres placed into interplate spaces, and the gas phase was air. The gas holdup in the RPC was influenced by: the vibration intensity, i.e., the power consumption, the superficial gas velocity, the solids content and the rheological properties of the liquid phase. The gas holdup increased with increasing vibration intensity and superficial gas velocity in both the two- and three-phase system. With increasing concentration of the CMC PP 50 solution (Newtonian fluid), the gas holdup decreased, because the coalescence of the bubbles was favored by the higher liquid viscosity. In the case of the CMC PP 200 solutions (non-Newtonian liquids), the gas holdup depends on the combined influence of the rheological properties of the liquid phase, the vibration intensity and the superficial gas velocity. The gas holdup in the three-phase systems was greater than that in the two-phase ones under the same operating conditions. Increasing the solids content has little influence on the gas holdup. The gas holdup was correlated with the power consumption (either the time-averaged or total power consumption) and the superficial gas velocity.

Agitation of a gas-solid-liquid system in a vessel with high-speed impeller and vertical tubular coil

2012 ◽  
Vol 66 (6) ◽  
Author(s):  
Marta Major-Godlewska ◽  
Joanna Karcz
Keyword(s):  
Power Consumption ◽  
High Speed ◽  
Gas Bubbles ◽  
Liquid System ◽  
Specific Power ◽  
Specific Power Consumption ◽  
Rushton Turbine ◽  
Agitated Vessel ◽  
Solids Concentration ◽  
Solid Liquid

AbstractExperimental results of gas hold-up, power consumption and residence time of gas bubbles in a gas-solid-liquid system produced in an agitated vessel equipped with a high-speed impeller and a vertical tubular coil are presented in this paper. Critical agitator speed, needed for the dispersion of gas bubbles and solid particles in liquid were also identified. The studies were carried out in an agitated vessel of the inner diameter D = 0.634 m and the working liquid volume of about 0.2 m3. A tubular coil of the diameter of 0.7D, consisting of 24 vertical tubes of the diameter of 0.016D, was located inside the flat-bottomed vessel. The agitated vessel was equipped with a Rushton turbine with six blades or an A 315 impeller with four blades. Both impellers had diameter, d, equal to 0.33D. The vessel was filled with liquid up to the height H = D. In this study, air and particles of sea sand with the mean diameter of 335 μm and the concentration of up to 3.0 mass % were dispersed in distilled water as the liquid phase. The measurements were carried out within the turbulent regime of the fluid flow in the agitated vessel. Results of the measurements were processed graphically and mathematically. Lower values of the critical agitator speed, n JSG, needed for simultaneous dispersion of gas bubbles and particles with the solids concentration from 0.5 mass % to 2 mass %, were obtained for the vessel equipped with the A 315 impeller. Higher values of the specific power consumption were reached for the vessel with the Rushton turbine. Higher values of the gas hold-up and residence time of the gas bubbles in the fluid were obtained for the system equipped with the Rushton turbine. Results of the gas hold-up as a function of the specific power consumption, superficial gas velocity and solids concentration were approximated with good accuracy using Eq. (5).

scholarly journals Determining the Effective Mass Transfer Area in Three-Phase Fluidized Bed with Low Density Inert Solids

2019 ◽  
Vol 70 (11) ◽  
pp. 4040-4046
Author(s):  
Simion Dragan
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Effective Mass ◽  
Fluidized Bed ◽  
Internal Diameter ◽  
Gas Velocity ◽  
Mathematical Correlation ◽  
Liquid Load ◽  
Three Phase ◽  
Solid Liquid

The absorption process is strongly influenced by the effective mass transfer area. In this study the effective mass transfer area in gas-solid-liquid three-phase fluidized bed was determined, in a fluidizing column having an internal diameter of 0.14 m and a height of 1.10 m. The solid packing is made of plastic hollow spheres of 0.01 m diameter, with 415 m2/m3 geometric area and a density of 170 Kg/m3. The absorption of carbon dioxide from the air-carbon dioxide mixture with molar concentration of 0.05M, 0.08M and 0.1M CO2 into sodium hydroxide aqueous solutions of 0.5N and 1.0 N has been employed as test reaction. The experiments were conducted with liquid load changing from 6.49 to 16.24 m�/(m� h) and gas velocity of 1.1 m/s and 2.1 m/s. It was found that the effective mass transfer area increased both with the increase of the gas velocity and the increase of the liquid spray density. It has been observed that the effective mass transfer area in gas-solid-liquid three-phase fluidized bed absorber is from three to eight times higher than the geometric area of the solid packing. A mathematical correlation has been established in order to predict the effective mass transfer area,under the specified conditions, with a deviation of less than 5%.

Experimental analysis of the hydrodynamics of a three-phase system in a vessel with two impellers

2012 ◽  
Vol 66 (6) ◽  
Author(s):  
Anna Kiełbus-Rąpała ◽  
Joanna Karcz
Keyword(s):  
Experimental Analysis ◽  
Gas Flow ◽  
Gas Bubbles ◽  
Liquid System ◽  
Internal Diameter ◽  
Phase System ◽  
Gas Dispersion ◽  
Rushton Turbine ◽  
Three Phase ◽  
Solid Liquid

AbstractResults of experimental analysis concerning gas hold-up and average residence time of gas bubbles in a three-phase gas-solid-liquid system produced in a baffled, double-impeller vessel are presented. Measurements were carried out in a vessel with the internal diameter of 0.288 m. Two different double-impeller configurations were used for agitation: Rushton turbine (lower) — A 315 (upper) and Rushton turbine (lower) — HE 3 (upper). Upper impellers differed in the fluid pumping mode. Coalescing and non-coalescing systems were tested. Liquid phases were distilled water (coalescing system) and aqueous solutions of NaCl (non-coalescing systems). The ability of gas bubbles to coalesce in the liquid was described using parameter Y. Dispersed phases were air and particles of sea sand. The experiments were conducted at seven different gas flow rates and two particle loadings. Effects of the ability of gas bubbles to coalesce (liquid phase properties), operating parameters (superficial gas velocity, impeller speed, solids loadings), and of the type of the impeller configuration on the investigated parameters were determined. The results were approximated mathematically. For both impeller configurations tested, significantly higher gas hold-up values were obtained in the non-coalescing gas-solid-liquid systems compared to the coalescing one. Out of the tested impeller systems, the RT-A 315 configuration proved to have better performance ensuring good gas dispersion in the liquid in the three-phase systems.

Parametric Study of Thermal Flow-Reversal Reactor for Ventilation Air Methane Oxidation

2013 ◽  
Vol 372 ◽  
pp. 406-409
Author(s):  
Hao Xin Deng ◽  
Yu Xin Wen ◽  
Qi Xiao ◽  
Yun Han Xiao
Keyword(s):  
Methane Oxidation ◽  
Residence Time ◽  
Methane Conversion ◽  
Methane Concentration ◽  
Fixed Bed ◽  
Experimental Studies ◽  
Flow Reversal ◽  
Fixed Bed Reactor ◽  
Thermal Flow ◽  
Gas Velocity

Experimental studies of ventilation air methane oxidation were carried out in a thermal flow-reversal reactor and a fixed bed reactor in laboratory scale respectively. The reaction characteristics of ventilation air methane in a fixed bed reactor were investigated. The influence of the feed gas velocity and the lean methane concentration on the temperature profile in the thermal flow-reversal reactor was studied. The internal temperature uniformity of the cross section and the cavity of the flow-reversal reactor which have influence on lean methane conversion have also been discussed and analyzed. The results shows that the oxidation of lean methane needs to meet the ignition temperature condition and the residence time condition, and the temperature distribution in the thermal flow-reversal reactor is mainly related to the methane concentration and the feed gas velocity while the methane conversion rate is mainly related to the temperature and the residence time in the high temperature zone of the reactor.

Determining the Effective Mass Transfer Area in Three-Phase Fluidized Bed with Low Density Inert Solids

2018 ◽  
Vol 70 (11) ◽  
pp. 4040-4046
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Effective Mass ◽  
Fluidized Bed ◽  
Internal Diameter ◽  
Low Density ◽  
Gas Velocity ◽  
Liquid Load ◽  
Three Phase ◽  
Solid Liquid

The absorption process is strongly influenced by the effective mass transfer area. In this study the effective mass transfer area in gas-solid-liquid three-phase fluidized bed was determined, in a fluidizing column having an internal diameter of 0.14 m and a height of 1.10 m. The solid packing is made of plastic hollow spheres of 0.01 m diameter, with 415 m2/m3 geometric area and a density of 170 Kg/m3. The absorption of carbon dioxide from the air-carbon dioxide mixture with molar concentration of 0.05M, 0.08M and 0.1M CO2 into sodium hydroxide aqueous solutions of 0.5N and 1.0 N has been employed as test reaction. The experiments were conducted with liquid load changing from 6.49 to 16.24 m³/(m² h) and gas velocity of 1.1 m/s and 2.1 m/s. It was found that the effective mass transfer area increased both with the increase of the gas velocity and the increase of the liquid spray density. It has been observed that the effective mass transfer area in gas-solid-liquid three-phase fluidized bed absorber is from three to eight times higher than the geometric area of the solid packing. A mathematical correlation has been established in order to predict the effective mass transfer area,under the specified conditions, with a deviation of less than 5%. Keywords: Effective mass transfer area, three-phase fluidized bed with low density inert solid packing, mass transfer model, chemical method, reaction regime

Hydrodynamics of Double-Dipleg Circulating Fluidized Beds for Waste Incineration

2003 ◽  
Author(s):  
Xiaoyin Yun ◽  
Weigang Lin ◽  
Shaohua Wu
Keyword(s):  
Fluidized Bed ◽  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Circulating Fluidized Bed ◽  
Waste Incineration ◽  
Pressure Profile ◽  
Gas Velocity ◽  
New Type ◽  
Superficial Gas Velocity

In order to solve the problems of high temperature chlorine induced corrosion and the emission of dioxins, a new type of double-dipleg circulating fluidized bed incinerator is under development at the Institute of Process Engineering, Chinese Academy of Sciences. Understanding the hydrodynamics of such new type of CFB incinerator are of crucial importance for successful design and operation of the system. Experiments have been carried out in a lab-scale double-dipleg circulating fluidized bed to study the hydrodynamics of such system. The investigation is focused on the pressure profile in the loop and residence time distribution of particles with different sizes and densities in the secondary dipleg. The results show that the pressure profile in such system is similar to that in the conventional CFB. The residence time distribution (RTD) function of particles in the second dipleg varies with particle recirculating rate, superficial gas velocity and the characteristics of the particles, such as density and size. The mean residence time of particles decreases sharply with an increase of the particle re-circulating rate and slightly decreases as the superficial gas velocity increases. It appears that the density of particle has a stronger influence on the residence time than the particle size. The lighter particles have a shorter residence time. The residence time distribution function of the particles is described by a tank-in-series model. The implication of the results to the design and operation of the double-dipleg circulating fluidized bed incinerator are discussed.

Numerical and orthogonal study on Optimization analysis of structure parameters of bubble breaker for Electrical Submersible Pump system

2021 ◽  
pp. 1-15
Author(s):  
Chuan Xie ◽  
Yonghui Liu ◽  
Xiaoping Li ◽  
Guangbiao Wang ◽  
Qinhua Wang ◽  
...  
Keyword(s):  
Slug Flow ◽  
Liquid Velocity ◽  
Bubble Diameter ◽  
Experimental Studies ◽  
Original Structure ◽  
Gas Velocity ◽  
Flow Conditions ◽  
Pump System ◽  
Superficial Gas Velocity ◽  
The Impact

Abstract Under slug flow conditions, electrical submersible pumps (ESPs) show a low efficiency due to Taylor bubbles, which cause pressure surging and gas pockets and the further deterioration of pressure boosting ability. In this study, a novel downhole bubble breaker is designed for mitigating the impact in ESP under slug flow conditions. The CFD-PBM coupled approach was employed to calculate the bubble breaker's average bubble diameter to evaluate its efficiency. Meanwhile, experimental studies were conducted and compared with numerical results. Also, MATLAB and DIP-image technology was employed to calculate the bubble diameter. Compared with experimental results, the simulation results agree well. Furthermore, the novel bubble breaker's performance was studied by orthogonal approach. The best result of range analysis is A2B3C4D1E4 (a = 30°, L = 300 mm, R = 2:1, vsg = 0.2 m/s, and vsl = 0.08 m/s), and sensitively analysis results present that the range of impact intensity are A (inlet angle) > E (superficial gas velocity) > B (total length) > D (superficial liquid velocity) > C (ratio of the gas–liquid channel). The optimal structure's bubble diameters are all less than that of the original structure, with a superficial gas velocity range of 0.2–0.6 m/s. The downstream bubble diameter of the optimal bubble is about 31.6% lower than the original structure at the maximum value point.

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